Description
Ta2NiS5 is a narrow gap semiconductor (Eg~0.39 eV) with suspected exciton insulator behavior like observed in its sister compound Ta2NiSe5. Excitonic insulators are novel material systems exhibiting correlated electronic phases. Condensation of excitons to its ground state happens for a specific condition when the exciton binding energy (Eb) is larger than the band gap (Eg). The excitonic condensation in semiconductors occurs through a Bose-Einstein condensation process, while the condensation in semimetals occurs through the Bardeen-Cooper-Schrieffer (BCS) process. The spontaneous band hybridization caused by the Coulomb attraction between the orthogonal conduction (electron) and valence (hole) bands opens the bandgap and drives the system into the insulating state
Properties of Ta2NiS5 crystals
| Crystal size | Needle form |
| Material properties | Direct gap 0.39 eV, excitonic insulator |
| Crystal structure | Cmcm |
| Unit cell parameters | a=0.341 nm, b=1.243 nm, c=1.509 nm; α=89.9°,β=89.7°, γ=75.54° |
| Growth method | Default: Flux zone growth (highest grade) Alternative: Chemical vapor transport CVT (lower grade) |
| Purity | 99.9999% confirmed |
Atomic structure of Ta2NiS5 crystals
Raman spectrum of Ta2NiS5 crystals
Additional Information
Elements: |
Ta,Ni,S |
Element: |
Tantalum |
Element: |
Nickel |
Element: |
Sulfur |
Formula: |
Ta2NiS5 |
Material class: |
M2YX5 |
Properties: |
Semiconductor |
Properties: |
Excitonic Insulator |
Band gap range: |
IR |
Growth method: |
Flux |
Growth method: |
CVT |
Doping: |
Undoped |
